A reappraisal of the carcinogenicity of surface modified asbestos fibres

Our plain-English summary of A reappraisal of the carcinogenicity of surface modified asbestos fibres, by P. Carthew, R.E. Edwards, B.M. Dorman, et al (Carcinogenesis, 1993).

The study

• Authors: P. Carthew, R.E. Edwards, B.M. Dorman, R.C. Brown, J.A. Hoskins, C.F. Simpson
• Journal: Carcinogenesis
• Published: 1993;14(11):2413-4
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A previous study using intrapleural administration of surface-modified amosite asbestos showed a difference in the number of pleural mesotheliomas induced with C18-hydrocarbon derivatised fibres compared to native amosite asbestos. The study has been repeated with larger groups of animals (30) under specific pathogen free conditions, resulting in an increase in the mean animal survival time for both fibre-treated groups. Under these conditions there was no significant difference between the numbers of pleural mesotheliomas induced by C18 hydrocarbon-modified amosite asbestos and native amosite asbestos. The major difference between the two studies was the mean time to death from tumour of rats exposed to fibres. The C18 amosite treated rats in the first study may not have had a mean survival time long enough to allow mesotheliomas to develop.

In plain English

This short communication re-examined the authors' own earlier rat experiment. That experiment had reported that amosite asbestos fibres given a C18 hydrocarbon surface coating (octadecyldimethylchlorosilane) caused fewer pleural mesotheliomas than untreated amosite. In the first study, 20 mg of fibre was injected into the pleural (chest) cavity of groups of 10 male Wistar rats. Pleural mesothelioma developed in 4 of 10 amosite-treated rats and in 1 of 10 rats given C18-modified amosite. The authors repeated the experiment with larger groups: 30 control, 29 amosite and 28 C18-modified amosite rats. These rats were kept free of common rodent infections. The fibre-treated rats lived longer than in the first study. Pleural mesothelioma developed in 8 of 29 amosite rats, 13 of 28 C18-modified amosite rats and none of 30 controls. The authors reported no significant difference between the two fibre groups. They concluded that their earlier statement that surface modification can affect the carcinogenicity of asbestos was incorrect, and that the C18 rats in the first study probably did not live long enough to develop tumours.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Animal experiment (lifetime bioassay with intrapleural injection) repeating the authors' earlier study with larger groups; published as a short communication
• Who was studied: Male Wistar rats. Study 1 (earlier, conventionally housed) used three groups of 10. Study 2 (specific pathogen free housing) used 30 control rats, 29 amosite rats and 28 C18-modified amosite rats.
• Exposure: Native (IUCC) amosite asbestos, or amosite surface-modified with octadecyldimethylchlorosilane (C18), injected into the pleural cavity at 20 mg of fibre per rat. Study 1 also included an octyldimethylchlorosilane (C8) modified amosite group.
• Main results:
  • Study 1 (earlier): 4 of 10 amosite-treated rats (and 4 of 10 C8-modified amosite rats) developed pleural mesothelioma, compared with 1 of 10 C18-modified amosite rats.
  • Study 2: pleural mesothelioma occurred in 0/30 control rats, 8/29 amosite rats and 13/28 C18-modified amosite rats.
  • In Study 2 the authors reported no significant difference in the number of pleural mesotheliomas between C18-modified amosite and native amosite.
  • Fibre-treated rats kept in specific pathogen free conditions (Study 2) had a longer mean survival time than the conventionally housed rats of Study 1.
  • Mean survival times reported for IUCC amosite-treated rats were 624 plus or minus 46 days in Study 1 and 646 plus or minus 41 days in the present study. A separate earlier study by other researchers reported 716 days. C18 amosite rats in Study 1 had a mean survival time of 650 plus or minus 38 days.
  • In Study 2, the mean time to death from tumour for C18-modified amosite rats was almost the same as the mean survival time of C18-modified amosite rats in Study 1.
• The authors' conclusion: The authors concluded that their earlier statement that surface modification can affect the carcinogenicity of asbestos was incorrect. They considered that the C18 amosite rats in the first study probably did not live long enough to develop tumours.
• Limitations the authors state:
  • The authors stated that a shortened lifetime of fibre-exposed rats, combined with small group sizes (as in their first study), could falsely make some groups appear to have fewer mesotheliomas.
  • The authors noted that survival time and time to death from tumour can vary from study to study, even with the same standardised amosite and the same strain and sex of rat.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Amosite, Pleural Mesothelioma, Mesothelioma.

Related studies

• Sorption of nonpolar aromatic contaminants by chlorosilane surface modified natural minerals — P. Huttenloch, K.E. Roehl, et al. (2001)
• Surface modification can affect the carcinogenicity of asbestos — R.C. Brown, P. Carthew, et al. (1990)
• In vitro biologic responses to native and surface-modified asbestos — N. Hahon, V. Vallyathan, et al. (1986)
• Differential release of superoxide anions by macrophages treated with long and short fibre amosite asbestos is a consequence of differential affinity for opsonin — I.M. Hill, P.H. Beswick, et al. (1995)
• Renal, vascular and cardiac fibrosis in rats exposed to passive smoking and industrial dust fibre amosite — P. Boor, S. Casper, et al. (2009)
• Bromo-deoxyuridine (BRDU) uptake in the lungs of rats inhaling amosite asbestos or vitreous fibres at equal airborne fibre concentrations — K. Donaldson, D.M. Brown, et al. (1995)

Browse more research in Carcinogenesis, or return to medical research.